As fossil fuels become scarcer and more expensive to extract and process, energy producers and users are becoming increasingly interested in other forms of energy. One such energy form that has recently seen a resurgence is wind energy. Wind energy is typically harvested by placing a multitude of wind turbines in geographical areas that tend to experience steady, moderate winds. Modern wind turbines typically include an electric generator connected to one or more wind-driven turbine blades, which rotate about a vertical axis or a horizontal axis.
One characteristic of conventional wind turbine blades is that they can attract potentially damaging lightning strikes. Accordingly, the wind turbine blade industry has developed techniques for mitigating lightning damage. FIG. 1A is a partially schematic, plan view of a representative conventional wind turbine blade 10 having a lightning protection system in accordance with the prior art. In particular, the wind turbine blade 10 can include a plurality of metallic or otherwise electrically conductive receptors 11 that are mounted flush or otherwise at the skin 12 of the blade 10. The conductive receptors 11 act as lightning rods during operation of the blade 10 to convey electrical current resulting from a lightning strike to the interior of the blade 10 and then to ground, and/or from ground to sky in the case of a ground strike.
FIG. 1B is a partially schematic, cross-sectional illustration of a portion of the blade 10, taken substantially along line 1B-1B of FIG. 1A. As shown in FIG. 1B, each receptor 11 can extend into the interior of the blade 10 and can be connected to an electrically conductive block 13. The conductive blocks 13 corresponding to each receptor 11 can be interconnected with a lightning cable 14. The cable 14 can extend along the length of each blade 10 to a hub of the turbine (not shown in FIGS. 1A-1B), and from the hub down the wind turbine pylon or tower to ground.
In general, larger (e.g., longer) wind turbine blades produce energy more efficiently than do short blades. Accordingly, there is a desire in the wind turbine blade industry to make blades as long as possible. However, long blades create several challenges. For example, long blades are heavy and therefore have a significant amount of inertia, which can reduce the efficiency with which the blades produce energy, particularly at low wind conditions. In addition, long blades are difficult to manufacture and in many cases are also difficult to transport. Still further, longer wind turbine blades present more exposed area and extend to higher elevations when in use, which increases the likelihood for a damaging lightning strike. Accordingly, a need remains for large, efficient, lightweight wind turbine blades, and improved methods for protecting such blades from lightning damage.